Method of reclaiming used foundry sand



Oct. 5, 1943.

M. OVESTRUD METHOD OF RECLAIMING USED FOUNDRY SAND Filed DBC.y 16, 1939 3 Sheets-Sheet 1 Oct. 5, 1943. M OvEsvTRUD. v 2,331,135

METHOD OF RECLAIMING USED FOUNDRY SAND Filed Deo. 16, 1959 3 Sheets-Sheet 2 tuto: MAJ s Oct. 5, 1943. M. ovl-:STRUD 2,331,135

IIVH''IOD OF RECLAIMING USED FOUNDRY SAND Filed nec. 1e, 1959 s sheetssheet s Neb/1L 01496 fr ad Patented Oct. 5, ,1943

2,331;1=35 METHOD F RECLASDIING USED FOUNDRY Melvin Ovestrud, Minneapolis, Minn., assigner, by

mesne assignments, turing Company to The Jeirey ui a corporation of ohio Application December i6, 1939, Serial No. 309,616 Claims, `/(Cl. 22-217) This inventionrelates an improved method4 of washing and screening sand used in foundries in the formation of steel castings.

in the manufacture of steel castings, impressions of the objects to be cast are made in specially prepared silica sand to form molds into which the molten steel ispoured to iorxn the castings or" desired shape. It has Lbeen found that it is'necessary that the silica sand,l even though it must he' packed solidly so as to withstand the hydraulic pressure of the molten metal, as well as the washing eiect of the iiowing metal while pouring, still must be porous enough to permit the escape of gases from the surface of the molten metal. lr" the silica sand is not porous enough to permit the esca-pe of the gases, these gases will enter into the surface of the molten steel and produce unsound steel castings characterized by gas bubbles in the suri'ace.-

The silica sand when new admirably meets the above requirements, but after a short period of use, even one or two times, the sand becomes relatively impervious and the continued use or" suchsand results in the formation of 'imperfect castings. rlfhis is due iirst to the breaking down of 'the sand particles exposed to the not steel and, secondly, to the ller or binding matterused in the sand while preparing the mold. As e. result it has been the custom heretofore to continually add new sand. to the molding sand after each exposure to the hot steel and'to discard the replaced sand. The replacement has usually been on the order of fifty to one hundred percent new sand, and it `will be readily appreciated that there has thus been a continued expense for new sand, aswell as for hauling away the spent sand.

the effort to avoid this constant huying'oi new sand and the expense of haulingeway the cid sand 'there have been attempts made to reclaim and recondition the old sand for use. Such operation is entirely feasible since the removal. of the fine, brokendown particles of the sand,

the dust-like binder material, and all lumps and similar particles will restore the sand to good condition with the required permeability. However, all such attempts heretofore made, with which .l' am familiar, have employed Aa.screening system in connectionwith a pneumatic cleaning apparatus. n other words, the 'sand' has been handled dry and in the removal of the very fine the occupational ills arising from such dust conditions. Of even more importance, however, it has been round that such pneumatic cleaning processes do not in fact produce a, sand having all characteristics of the new sand, and it has been necessary to continue the addition of new sand even if in smaller quantities.

Having in mind the foregoing it is the primary object of my invention to provide a method whereby spent foundry sand may b reconditioned and made ready for use again with as good results as would obtain in the use of new sand.

Another and important object is to provide a method for thus reclaiming spent 4foundry sand which operates with water es the cleaning methus eliminating in one stroke all dicul- 1 ties with dust in the operation.

A furtherohject is to provide a method for this purpose which will operate at least serni- 'automatically with only occasional attention and atlittle vexpense so that 'the reclaiming of 'the spent sand will he far less expensive than the condustparticles .a dust condition has been set up '.'ffwhichjin actual practice, has required either a ','very'elaborate and expensive dust collecting system in the plant lor has exposed the workers to tinued buying of new sand. n

These and other more detailed and specified objects will loe disclosed in the courseof the following specification, reference being had to the accompanying drawings, in whichiiig. l is a side elevation of an apparatus constructed in accordance with my invention and showing the same in operative condition..

Fig. 2` is a fragmentary detail sectional View along the line in Fig. l, showing the drive meansliorthe dehydratcr and conveyor.

Fig. 3 is en enlarged vertical and longitudinal section through my apparatus, a portion of the 4i'eeder conveyor being broken away.

Fig. l isa top plan view or the structure shown in Fig. 3. K

Fig. 5 is a cross sectional detail view along the line 5 5 in Fig. 4, showing the screen and outlet opening in the end lig. 6 is a cross sectional the washer and along the line s--S in Fig. fi.

Referring now with more particularity to the drawings, in my improved method therey is used apparatus which comprises as its main units a frame A, a scrubber and washer B, screen C, elutriation tank D, and dewatering or dehydratlng conveyor E, all of which are-assembled in compact and cooperative arrangement as shown. Units D and E together constitute a liquid or hydraulic separator and dehydrator.

The said. frame A is madeup of suitable structural beams including a base l, upstanding post detail view through of the scrubber. i I

associated trarne parts, taken these ends the drum carries a series of .the opposite, lower 8 and upper parallel channels or members 9 all rigidly secured together in accordance with usual practise in such constructions.

'Ihe scrubber B and screen C are assembled and operate as a unit and will be rst described in detail. Said scrubber takes the form'of an elongated imperforate drum or cylinder I having inwardly t'urned end flanges II which form large inlet and outlet openings I2 and I3. This drum is supported in an endwise inclined position in the frame A upon rollers I4 attached by bearings I5 to the upper parallel frame members 9 so that said drum may rotate freely about its longitudinal axes above said frame. The inclination of the drum is such that it slopes downwardly from the inlet end toward the outlet end. Intermediate spaced inwardly turned, annular partition flanges or rims I6, the inner edges of which form large center openings as show'n, and between the end flanges Il and these partition anges are provided a series of inwardly and radially turned, longitudinally extended scrubbing blades or nights I1.

The screen C is also cylindrical but of .larger .diameter than the washer B and the'perforate I8 is secured coaxially and endwise 'on the lower delivery end of the drum' I0 by an outwardly turned circumferential rim I9 which joins the parts and prevents the escape'of 'water or sand at the junction. The drum thus opens :directly into one end of the screen and delivery end of the screen is 4left entirely open as shown.

A feed or receiving hopper 20 is mounted b`y frame members 2l `on the end of the frame A cylindrical wall in an inclined position so that its spout'22 will `enter' the inlet opening I2 of the 'scrubber`1B. I

-The spent sand is fed to the open upper 'end of 'this hopper by any suitable means such'as Va conventional bucket type conveyor 23,: andthe sand may of course flow by gravity into the scrublarge beveled lring ber. A spray pipe 24 is arranged in the hopper '20 to`spraythe sand with water as 'it enters and a control'valve 25 is provided for controlling the spray'.

A delivery spout 26 for the oversize material is'supp'orted in the frame outwardly of,' `and beneath, the open lower end of the screen C in position to receive material ejected from said :screen and deposit the same either upon the -ground as shown, or upon a conveyorlor other means for carrying it away.

Supported in the frame immediately below the screen and scrubber elements is the elutriation tank D having a large opening 28 in its top-29 to receive material passed directly downward through the screen C. 'I'he bottom 3llvof` the -tank21 inclines 'upwardly from the receiving end to a point beneath the receiving end of the scrubber B and this bottom is of semi-circular cross section to nt the spiral screw-type de- .waterlng or dehydrating conveyor E which is mounted along said bottom. The tank infact hasa cylindrical or tubular extension 9| enclosing the upper end portion of the conveyor E and this extension terminates in a downwardly opening delivery spout 32 disposed overa hopper and conveyor mechanism 33; for carrying oil the cleanedand dehydrated material. The spout openingor discharge point of the conveyor E 20. The pipe or spray means shown, for example, as,

in its end wall 36 which opens into a side delivery conduit 31 for ca' g away waste water, and the water level in the tank may be controlled by a vertically adjustable Weir or gate 38 movable over-'said opening 35. A water spray pipe 39 is arranged in the tank in an inclined position over the conveyor E and has Jet openings 40 for discharging water upwardly below the normal water level L and against the downward fall of sand from the screen C, the pipe entering laterally through the side wall 4I of the tank and being provided exteriorly with a control valve 42. These water iets 40 are located immediately inward of the weir 38 and extendv along the pipe the full width of the sheet or stream of sand falling from the screen C, being thus extended approximately the full length of the screen itself and in the same vertical plane, as shown in Fig. 3.

The various working parts are driven by a suitable prime mover, as for example the electri motor 43 which rotates a'main countershaft 4 through the belt and pulley mechanism 46. A scrubber drive shaft 46 is journaled transversely in the frame in bearings 41 in spaced relation to the discharge end of the screen C and is rotated by sprocket chain assembly 48. A pinion 49 on'this shaft 46 drives a gear 50 on the shaft of which is a-beveled pinion 5| meshed with a gear 52 supported as by brackets 53 in coaxial relation but in axially spaced position with respect to the screen C. A large guard disk 54 backing up this gear 62 prevents material elected from the screen from coming in contact with the gears and at the same time guides said material downwardly to the spout 26. The aforesaid drive lmechanism will of course rotate the entire scrubber and screen mechanism upon its axis and upon the rollers I4. 'Ihe ring gear 62 has its shaft journaled in a bearing 62a on the frame to support the lower end of the screen and scrubber unit.

Also driven Afrom the main countershaft 44,

by, sprocket chain mechanism 55, is a second L at its end carries a bevel-pinion 59 meshing with a similar pinion 60 in the upper end of the shaft 6I of conveyonE to thereby rotate said conveyor -in a'direction causing its spiral blade to carry materialupwardly along the tank bottom I9 toward the spout 32.

The .conveyor 23 may also be conveniently driven from the shaft 61 by sprockets and chain 92 as clearly shown. In Fig. 1 this conveyor is directed into a pit 6I wherein is located a feed hopper 94 of conventional form.

In operation the spent or used sand is dumped into the feed-hopper 94 Afrom which it' is fed to conveyor 23 andthen dumped into the hopper 24 then sprays the dirty sand and washes it through spout 22 into the scrubber B at Vthe same time filling the scrubber with water, and the sand, to the level of the lower edge of the delivery opening I9. As the drum I9' rotates, this mass of water and sand is carried upwardly by the bafiles I1 and given a is constricte'd by an upwardly inclined wing'or vane 94, for a purposewhich will appear.

The-deeper end of the tank D immediately beneath thescreen C has an overflow opening 35 Most lumps are thus disintegrated, and as the material flows onto the screen C the material of proper size will drop straight through dow-n into the tanl; D. 'I'he larger particles such as lumps and trash will be screened out and discharged from the open end of the screen into spout 26 for disposal. -f

'I'he material falling into the tank D is thus all of desired size and smaller, and the "lines" such asvbroken down sand particles, binder and like material, will be put in suspension and may iiow off through the conduit 31, the elutriation process being facilitated, and the sand further cleaned, by admission of clean rinsing water by pille 39.

In such operation the water iets 4I thoroughlyV agitate the full sheet or body of sand as it falls into the tank and these jets, being located near the Weir 38 8nd directly in the strata of water flowing over the same, will obviously aid also in carrying the nes over said weir. l

The heavier particles of sand falling to the bottom of the tank D are picked up by conveyor E and are can'ied thereby up along said bottom and finally discharged at spout 32 onto conveyor 33 for transmission thereby to storage pile or bin. As the sand reaches the spout 32 it is squeezed by the wing 3| so that the water is forced out and allowed to ilow back to the tank while the dehydrated sand is carried on out.

As heretofore stated, permeability is the most important characteristic of sand used for molding purposes. It has been found that after the sand has been exposed to the hot steel, it has to be remixed with a certain proportion of new unused sand in order to maintain a required minimum permeability. 'I'his is partly due to the breaking down of the sand particles when in contact with the molten steel, but is chiefly ou account of a tendency of the binding ingredients used in the sand to fill up the voids -between the component sand particles, with the result that the sand will not permit the gases to escape and will cause the appearance of gas pockets as well as rough blemishes on the castings.

It is evident that by the removal of these line particles of broken down sand and binder material, as well as larger lumps and trash, that the residue of the sand, constituting byfar the greater part of its bulk, may be made completely iit for use 8811111, and this process is carried out admirably by my apparatus and method disclosed herein. In fact due to the thoroughness in which the sand is washed and the nes removed, the

reclaimed sand is found to have even a higher degree of permeabilitythan the new sand.

My method is seen to lbe simple and capable of inexpensive continuous operation so that the cost of reclaiming the sand may in f act be less than the disposal of the sand at some remote dump might be.

The reviving of the used sand in the apparatus is accomplished by what I believe is an entirely new method. This involves initially spraying.

t a ofthe sand and scrubbing and tumbling the mixture of sand and water so that the'binder and line materials in the sand are put in suspension, screening `the sand to remove all lumps and large 5' particles, rinsing the sand and floating olf all binder materials and nes, .and nally dehydrating and delivering the completely washed and revived sand for further use.

jThe superiority of this method over previous ones using air for removing the 'nes vare apparent and should need no further delineation herein. v

It is understood that suitable modifications .may be made inthe structure as disclosed,'pro

vided such modifications come within the' spirit and scope, of the appended claims. Having nowA Y therefore fully illustrated and described my inventiom what I claim to be newand desire to protect by Letters Patent is:

l. The method of treating' used foundry sand,

comprising scrubbing the sand in a liquid bath Ito separate pure sandf from foreign matter, screening the wet sand and foreign matter to remove foreign matter of large size, treatingthe screenings in a liquid gravity separator to produce products of usable sand and foreign matter, and directing the separated products along dii-v lferent paths. Y 2. 'I'he method of treating used foundry sand,

comprising scrubbing the sand inV a liquid bath to separate pure sand from foreign matter, screening the wet sand and'foreign matter to remove foreign matter of largesize, treating the screenings in a hydraulic separator to produce products of usable sand and foreign matter. di-

recting the. separated productsalong different paths, and dehydrating'the usable'sand.

3. 'I'he method of treating used foundry sand which 4comprises recovering used sand, disinte- 4'0 grating pieces of adhering' sand particles, scrubb'ing the sand particles in a liquid bath to remove foreign matter adhering thereto, separating the cleaned sand and foreign matter by hydraulic gravity separation, and dehydrating and 5 recovering the cleaned sand.

4. The method of treating used foundry sand. comprising scrubbing the sand in a liquid bath to separate -pure sand from adhering foreign matter, screening the wet sand and foreign matter to remove foreign matter of large size.' treating the screenings in a hydraulic separator to produce products of usable sand and foreign matter, and directing the separate products along different paths.

s 5. The method of treating used foundry sand.' 5 comprising scrubbing the sana m a liquid bath to separate pure sand from foreign matter screening the wet sand and foreign matter to re:

move foreign matter of large size, treating the screenings in a separator to produce products of 00 usable sand and foreign matter, and

the separate products along diii'erent paths.

MELVIN OVESTRUD. 

